The disgrace is that the Mets had 22 years to do the right thing based on performance, based on accomplishment, based on Gary Carter’s inviolable place in the collective heart of their fans. He is a Hall-of-Fame player who played the meat of his prime as a Met. He was the missing piece to a championship puzzle.

On a team forever remembered as much for its indefatigable bacchanalia as its baseball, Carter was one player you never feared would break the fans’ covenant of faith. He spent far more time in chapel and trainer’s room than saloon or casino. And from the moment the Mets released him on Nov. 14, 1989, there should’ve been a plan to invite him back for a Day, capital “D,” to put his number 8, forever, on the wall.

The Mets, being the Mets, never did that.

The Mets, being the Mets, have treated that 1986 team with a curious blend of indifference and aloofness. By this time, by the 25th anniversary of their second world championship, the Mets should’ve retired 8, and they should’ve retired Keith Hernandez’s No. 17, together or separately. But this is a team that opened a new ballpark two years ago without a trace of its own history preserved anywhere within its walls, had to be guilted into finally acknowledging that it even had a history.

Carter is sick now, news that has devastated the Mets’ family and fan base. And the Mets face a disquieting choice now. Even an operation as tone-deaf as this ought to know that it should finally step up and do the right thing, have a day sometime in the next few months, put Carter’s 8 up on the wall next to 37, 14, 41 and 42.

Would it look like they would be reacting to the horrific news of Carter’s brain cancer? Maybe. And you know what? That’s tough. The Mets could’ve done the right thing on their own years ago. Now they need to give their fans an opportunity to thank and salute Carter, whether he is physically up for the task or not. And because the Mets couldn’t identify the right thing to do if it was a neon sign, then shaming them into doing the right thing will have to do.

Here’s the thing you have to remember about the men who currently own the Mets: It isn’t only the big things they have shown a talent for bungling though the years — bad player choices, bad salary approvals, Art Howe’s high-wattage personality. It’s also a series of small things they almost always get wrong.

They have no idea how to connect with fans, and seemingly no concern that they don’t. Fans have been clamoring for 8 and 17 to be retired for years, and yet they keep being distributed to the likes of Desi Relaford and Dae-Sung Koo. The issue never has come close to making it out of committee meetings where people with no feel for this always trump those who do. Par for the course.

The Wilpons must realize why people reacted so favorably to that old snapshot of David Einhorn wearing his Dave Kingman jersey from 1976: Finally, there is a connection between the owner’s suite and the Pepsi porch. If Jeff Wilpon cared a whit about any of this, at some point in the last 20 years he might’ve, say, recited the Mets’ opening-day lineup from 1980, the year his old man took over the team.

The Mets’ PR gurus have simply no clue how much hearing The Scion say, “Tavares-Maddox-Mazzilli-Henderson-Jorgensen-Stearns-Morales-Flynn-Swan” would’ve nourished Mets fans through the years, made them feel differently about Jeff, even if he had to look it up. It’s far too late for that now, the disconnect between the Wilpons and the fans too complete — unless you still own an old Brooklyn Dodgers cap, anyway.

What you look for now are signs, hints that they get it. Having Gary Carter Day — for kicks, let’s say July 19, 20 or 21, against the Mets’ old rivals from St. Louis — would be a fair starting point. Retiring 8 is the right thing to do.